Automatic balancing measuring meter

ABSTRACT

An automatic balancing measuring meter is comprised by a magnetic core including an input, an output and a positive feedback windings wound thereon, a movable magnet providing a magnetic flux corresponding to the angle of rotation thereof, an amplifier including a tuning circuit connected to the output winding, a feedback circuit to apply a portion of the output from the amplifier to the positive feedback winding, a detector to detect the output from the amplifier, and torque generating means energized by the detector to drive the movable magnet to cause the flux produced by the movable magnet to balance with the flux produced by the input winding.

' [72] Inventors: Takshi United States Patent Yamanaka et al.

[54] AUTOMATIC BALANCING MEASURING METER Yamanaka; Rinichi Miyauchi;Hisaya Eqiita; Nobuo Kaieda, all of Tokyo, Japan [73] Assignee: YokogawaElectric Works, Ltd.,

Tokyo, Japan [22] Filed: April 2, 1970 [2]] Appl. No.: 25,023

521 US. Cl. ..324/99 R, 324/117 R 51 Int. Cl. ..G01r 17/06, GOlr 33/00[58] Field 6: Search ..324/99, 100, 117 R, 120;

[56] References Cited UNITED STATES PATENTS 2,154,260 4/1939Brandenburger ..324/99 x 2,446,390 8/1948 Rath ..324/99 2,586,686 2/1952Medlock ..324/99 1451 Nov. 28, 1972 2,347,200 4/1944 Lehde, ..324/99 X2,053,154 9/1936 La Pierre .......324/1l7 R 3,396,338 8/1968 Buchanan etal. .....324/ 120 X Primary Examiner-Rudolph V. Rolinec AssistantExaminerErnest F. Karlsen Attorney-Chittick, Pfund, Birch, Samuels &Gauthier ABSTRACT An automatic balancing measuring meter is comprised bya magnetic core including an input, an output and a positive feedbackwindings wound thereon, a movable magnet providing a magnetic fluxcorresponding to the angle of rotation thereof, an amplifier including atuning circuit connected to the output winding, a feedback circuit toapply a portion of the output from the amplifier to the positivefeedback winding, a detector .1 to detect the output from the amplifier,and torque generating means energized by the detector to drive themovable magnet to cause the flux produced by the movable magnet tobalance with the flux produced by the input winding.

4Clains,7Drawing Figures SHEET 1 0F 3 INVENTOR s ATTORNEY I TAKASHIYAMANAKA RINICHI MIYAUCHI HISAYA FUJITA OBUO KAIEDA P'A'TE'N'TED nnv 28I972 SHEET 3 [IF 3 PATENTEDNUVN'ISIZ m wl TAKASHI YAMANAKA RINICHIMIYAUCHI INVENTOR HISAYA FUJITA NOBUO KAIEDA 2 Y .RWQA cfx m q: 6 aMiQA/ATTORNEY BACKGROUND OF THE INVENTION net and an input winding,respectively is disclosed in US. Pat. No. 2,053,145 or Japanese Pat. No.127,165.

SUMMARY OF THE INVENTION It is an object of this invention to improvethis well known type of automatic balancing measuring instrument.

Another object of this invention is to provide a servometer of simpleconstruction andhigh gains which does not require an independent ACsource or an oscillater and the like.

The automatic balancing measuring apparatus constructed according to theprincipal of this invention comprises a magnetic core, an input winding,an output winding and a positive feedback winding which are wound onsaid core, a movable magnet providing a magnetic flux for said core ofthe value corresponding to the angle of rotation of said movable magnet,an amplifier including a tuning circuit connected to said outputwinding, a feedback circuit to apply a half wave rectified portion ofthe output from said amplifier to said positive feedback winding, adetector circuit to detect the output from said amplifier, and torquegenerating means connected to the output from said detector circuit todrive said movable magnet to cause said flux in said core provided bysaid magnetic core to balance with the flux produced by said inputwinding.

In accordance with another aspect of this invention there is provided anautomatic balancing apparatus comprising a magnetic standard including amagnetic core provided with an input winding, an output winding and apositive feedback winding, and a movable magnet providing for saidmagnetic core a flux of a value corresponding to the angle of rotationof said movable magnet; a self-oscillation amplifier including anamplifier to amplify the output from said output winding of saidmagnetic standard, and a circuit to positively feedback the output fromsaid amplifier to said positive feedback winding; a rectifier to rectifythe output from said self-oscillation circuit; and a forcing coilsupplied with the rectified output from said rectifier to mechanicallydrive said movable magnet until a balanced position is reached wheresaid flux provided by said movable magnet and the flux provided by saidinput winding balance each other.

Preferably a rate coil is associated with the forcing coil to detect therate of change in the moving speed of the forcing coil to provide abraking force thereto.

BRIEF DESCRIPTION OF THE DRAWING The invention can be more fullyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 shows a connection diagram of one embodiment of the novelautomatically balanced measuring instrument;

FIG. 2 shows a characteristic curve of a servo-amplifier utilized inthis invention;

FIG. 3 is a connection diagram of a modified embodiment of thisinvention; a

FIG. 4 is a plan view of an assembly of a magnetic standard, a forcingcoil and a rate coil;

FIG. 5 is a sectional view of the assembly taken along a line V V inFIG. 4;

FIG. 6 shows a side elevation and FIG. 7 shows the rear view of theassembly shown in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to theaccompanying drawing a preferred embodiment of the novel automaticbalancing measuring'instrument illustrated in FIG. 1 comprises anamplifier A connected to receive a DC input signal through inputterminals INPUT and a magnetic standard I including a magnetic core T, amovable magnet M and a-DC input winding 1 an output winding 1 and apositive feedback winding 1:, which are wound upon the magnetic core T.The measuring instrument further comprises an amplifier circuit 11including a tuning circuit which includes an amplifier transistor Tr,,an output transformer T and an output condenser C which cooperates withthe input winding of transformer T, to constitute the tuning circuit,and a detector amplifier III including detector diodes D and D resistorsR R and R bias resistors R and R and amplifier transistors Tr and Tr;,.Further, a torque motor IV is provided comprising an exciting winding 1,a moving core or a rotor F and a balancing spring S connected to therotor F. DC power is supplied to the measuring instrument from a DCsource E, and a multivibrator MV is provided to convert the output ofthe source E into an alternating current which is supplied to theamplifier A through an input winding 1 and an output winding 1 Thus, theinput terminals INPUT for the DC voltage 1 are connected to the inputwinding 1 of the transformer T of the magnetic standard I via the DCamplifier A. Output winding 1 of transformer T is coupled to.

the input of the tuning amplifier circuit II and the output thereof isconnected to the input of the detector amplifier III and to the positivefeedback winding 1 of transformer T. The output of the detectoramplifier III is connected to the exciting winding 1 of the torque motorIV. As shown by dotted lines the moving magnet M of the magneticstandard I is driven by the rotor F of the torque motor IV.

The novel automatic balancing measuring instrument operates as follows:

Upon application of the half wave rectified voltage from the tuningamplifier II to the feedback winding 1 of the transformer T of themagnetic standard I, an AC voltage will be produced in output winding 1of transthus here operating as a saturable reactor. Thus, the V ACsignal supplied by the output winding 1 and the signal applied to thepositive feedback winding 1 have the same frequency. The AC outputsignal from the output winding 1 of the transformer T is amplified bythe tuning amplifier II and therectified half wave obtained from aportion of the amplified signal is applied to the positive feedbackwinding 1 Thus, the tuned amplifier II comprises a portionof a feedbackoscillator in cooperation with transformer T whereby to increase theoscillation output and hence the output voltage in proportion to asignal corresponding to a given polarity of the difference flux Ad).However, as the polarity of this difference flux is reversed. Theoscillation is stopped. The oscillation output of the tuning amplifierII is detected by diodes D, and D of the detector amplifier Ill and isthen amplified bytransistors Tr and Tr to provide an output signalcontaining ripples. The output from. the detector amplifier III issupplied to the exciting coil 1 of the torque motor IV. However, as thefrequency of the ripples contained in the output is high, the torquemotor responds only to the DC component.

FIG. 2 shows the relationship between the DC current 1', supplied to theinput winding l of the magnetic standard I and the output DC current isupplied to the exciting winding 1 of the torque motor IV. As can benoted from FIG. 2 as the input current 1', increases, the output DCcurrent i also increases correspondingly to increase the torque of therotor F of the torque motor IV. Increase in the torque of the rotor Fresults in a rotary movement of the movable magnet M of the magneticstandard I until a balancing position is-reached at which the fluxproduced by DC current i, supplied to the input winding 1, and the fluxsupplied to the core of transformer T from the moving magnet M balanceeach other. Conversely decrease in the input DC current causes decreasein the output current i whereby the rotor M is rotated in the oppositedirection by the force of spring S until a new balancing position isreached where the flux produced by the input current i, and the fluxsupplied by the moving magnet M again balance each other. In thismanner, it is possible to display the displacement corresponding to theinput DC signal in terms of the positionof the rotor F of the torquemotor or the position of the movable magnet M of the magnetic standard.

In the modified embodiment shown in FIG. 3 the DC input signal i issupplied across input terminals I, and I In this embodiment, themagnetic standard M is shown as comprising a saturatable magnetic core Ca movable magnet M disposed in an air gap of the core C to produce amagnetic flux in the core of the magnitude proportional to the angle ofrotation of the magnet, and an input winding n an output winding n and apositive feedback winding n The output winding n is shunted by a tuningcondenser C and is connected to an oscillation amplifier A A transformerT is provided having an input winding n energized by the output from theoscillation amplifier A, through feedback winding n and an outputwinding n connected to a rectifier D. The output of the rectifier D issupplied to a forcing coil C rotatable in a uniform unidirectional fieldand a rate coil C cooperating with the forcing coil, respectively,through amplifiers A and A The forcing coil C is normally biased by aconstant force supplied by a spring S. The output of the rate coil C isnegatively fed back to the input of the amplifier A through theamplifier A A source of direct current. B provides necessary power toamplifiers A A and A The modified embodiment shown in FIG. 3 operates asfollows. More particularly, the magnetic standard M is constructed suchthat the flux Y produced in the core C by the input DC current i, andthe flux d produced in the core C by the movable magnet M have oppositedirections, and that if fluxes d), and are not equal and hence toproduce a difference flux A the output winding n provides an outputvoltage of the magnitude corresponding to the difference flux Arb. Theoutput voltage from the output winding n is amplified by the amplifierA, and the amplified output is supplied to the input winding ri oftransformer T via the positive feedback winding n As a result, thecircuit comprising the output winding m amplifier A and the positivefeedback winding n of the magnetic standard M performs aself-oscillation, the oscillation frequency thereof being determined bythe inductance of the output winding n and the capacitance of the tuningcondenser C. Whilethe amplitude of the output of the self-oscillationcircuit increases corresponding to the magnitude of the difference fluxA4), when the polarity of the difference flux A45 reverses theoscillation stops. The output from the self-oscillation circuit isrectified by the rectifier D and is then amplified by the amplifier AThe amplified DC output i is supplied to the forcing coil C If thetorque produced by the DC output i exceeds the force of spring S, theforcing coil is rotated by a torque proportional to the difference.Rotation of forcing coil C causes movable magnet M A to rotate until abalanced position is reached where the flux 4), produced by the input DCcurrent i, and the flux qb produced by the moving magnet M balance witheach other. Conversely as the input DC current i, is decreased todecrease the output DC current i to decrease the torque produced by theforcing coil C to a value less than the force of spring S, the forcingcoil C (and hence the movable magnet M is rotated in the oppositedirection in proportion to the difference between its torque and theforce of spring S until a new balanced position, is reached at which.the flux 4),

produced by the input DC current i, and the flux produced by the movingmagnet M again balance each other. Thus, according to this invention, itis possible to display the displacement which van'es in accordance withthe magnitude of the input DC current i, in terms of the position of theforcing coil C or of the moving magnet M Furthermore the rate coil Ccooperating with the forcing coil C produces a voltage proportional tothe speed of rotation of the forcing coil C to negatively feedback thisvoltage to the input of amplifier A thus applying an appropriate brakingforce to the rotary movement of the forcing coil C with simpleconstruction.

FIGS. 4 to 7 inclusive show a preferred construction of an assembly ofthe magnetic standard, the forcing coil and the rate coil. FIG. 4 showsa plan view of the assembly, FIG. 5 is a sectional view of the assemblytaken along a line V V in FIG. 4, FIG. 6 shows a side elevation and FIG.7 shows a rear view of the assembly. In FIGS. 4 to 7, elementscorresponding to those dipicted in FIG. 3 are designated by the samereference numerals. The assembly comprises a rotary shaft, a movablecoil 2 including the forcing coil C and the rate coil C which are woundon the same frame secured to the shaft 1 by means of a supporting disc3, a weight 4 attached to the supporting disc 3 to balance the weight ofmovable coil 2, a magnetic core 5 linking the movable coil 2, a U shapedyoke 6 interconnecting the opposite ends of the core 5 and a permanentmagnet 7 lying along the yoke 6. When energized by the input DC i (FIG.1), the movable coil 2 rotates to the right or left as viewed in FIG. 4about shaft 1 in an air gap defined between core 5 and magnet 7 torotate therewith the movable magnet M of the magnetic standard M securedto the shaft 1. An output arm 8 is secured to the opposite end of shaft1 and is connected to one end of a spring S, the opposite end thereofbeing connected to an adjusting lever 9. A stop 10 is secured to a baseplate 11 of the assembly to limit excessive movements of the output arm8. With this assembly it is possible to display the rotationaldisplacement of the movable coil 2 or movable magnet M in terms of thedisplacement of the output arm 8. Consequently, it is possible to recordor indicate the value of the input current 1', by connecting the outerend of the output arm 8 with a suitable recording mechanism or anindicating mechanism, not shown.

Thus, the novel automatic balancing measuring instrument can operate athigh accuracies because it utilizes a movable permanent magnet as themagnetic standard. Morecover since the signal detection circuit of themagnetic standard includes an oscillator and an amplifier, it is notnecessary to provide an independent AC source and oscillator, thusgreatly simplifying the circuit construction.

Although the output signal from the above described oscillationamplifier acting as an amplifier and an oscillator has only onepolarity, when combined with a movable core type torque motor or amovable coil type torque motor provided with a balancing spring as shownin FIG. 1 or 3, the oscillation amplifier constitutes an automaticbalancing type measuring instrument which is simple and inexpensive.Moreover, the novel measuring instrument can operate with a DC sourcealone without the necessity of providing an AC source for excitation asin the prior art apparatus. Further, since the input terminals areisolated from the source, the novel instrument is suitable for use inmany industrial applications. Mounting of the forcing coil and themoving magnet of the magnetic standard on the common rotary shaftgreatly simplifies the construction, thus providing a balancingapparatus of small size and compact construction. Further, by mountingthe rate coil on the same frame as the forcing coil to utilize theoutput of rate coil as the braking force, the braking characteristics ofthe automatic balancing measuring instrument can be improved.

While the invention has been shown and described in terms of preferredembodiment thereof, the invention is not limited to these embodimentsand many changes and modifications will be obvious to one skilled in theart without departing from the true spirit and scope of the invention asdefined in the appended claims.

What is claimed is: v

1. An automatic balancing measuring instrument comprising a saturablemagnetic core, an input winding, an output winding and a positivefeedback winding which are wound on said core, a movable magnetproviding a magnetic flux for said core of the value corresponding tothe angle of rotation of said movable magnet, an amplifier including atuning circuit connected to said output winding, a feedback circuitincluding a half wave rectifier to apply a portion of the output fromsaid amplifier to said positive feedback winding, a detector circuit todetect the output from said amplifier, and torque generating meansconnected to the output from said detector circuit to drive said movablemagnet to cause said flux in said core provided by said movable magnetto balance with the flux produced by said input winding.

2. An automatic balancing apparatus comprising a magnetic standardincluding a saturable magnetic core provided with an input winding, anoutput winding and a positive feedback winding, and a movable magnetproviding for said magnetic core a flux of a value corresponding to theangle of rotation of said movable magnet; a self-oscillation amplifierincluding an amplifier to amplify the output from said output winding ofsaid magnetic standard, and a circuit to positively feedback the outputfrom said amplifier to said positive feedback winding; a rectifier torectify the output from said self-oscillation circuit; and a forcingcoil supplied with the rectified output from said rectifier tomechanical drive said movable magnet until a balanced position isreached where said flux provided by said movable magnet and the fluxprovided by said input winding balance each other.

3. The automatic balancing apparatus according to claim 2 wherein saidmovable magnet and said forcing coil are mounted on the same rotaryshaft.

4. An automatic balancing apparatus comprising a magnetic standardincluding a saturable magnetic core provided with an input winding, anoutput winding and a positive feedback winding, and a movable magnetproviding for said magnetic core a flux of a value corresponding to theangle of rotation of said movable magnet; a self-oscillating circuitincluding a first amplifier to amplify the output from said outputwinding of said magnetic standard, and a circuit for positively feedingback the output from said first amplifier to said positive feedbackwinding; a rectifier to rectify the output from said self-oscillationcircuit; a second amplifier to amplify the output from said rectifier; aforcing coil responsive to the output from said second amplifier todrive said movable magnet until a balanced position is reached wheresaid flux provided by said movable magnet and the flux provided by saidinput winding balance each other; a rate coil wound on the same frame assaid forcing coil; and means to negatively feedback the output from saidrate coil to the input of said second amplifier.

1. An automatic balancing measuring instrument comprising a saturablemagnetic core, an input winding, an output winding and a positivefeedback winding which are wound on said core, a movable magnetproviding a magnetic flux for said core of the value corresponding tothe angle of rotation of said movable magnet, an amplifier including atuning circuit connected to said output winding, a feedback circuitincluding a half wave rectifier to apply a portion of the output fromsaid amplifier to said poSitive feedback winding, a detector circuit todetect the output from said amplifier, and torque generating meansconnected to the output from said detector circuit to drive said movablemagnet to cause said flux in said core provided by said movable magnetto balance with the flux produced by said input winding.
 2. An automaticbalancing apparatus comprising a magnetic standard including a saturablemagnetic core provided with an input winding, an output winding and apositive feedback winding, and a movable magnet providing for saidmagnetic core a flux of a value corresponding to the angle of rotationof said movable magnet; a self-oscillation amplifier including anamplifier to amplify the output from said output winding of saidmagnetic standard, and a circuit to positively feedback the output fromsaid amplifier to said positive feedback winding; a rectifier to rectifythe output from said self-oscillation circuit; and a forcing coilsupplied with the rectified output from said rectifier to mechanicaldrive said movable magnet until a balanced position is reached wheresaid flux provided by said movable magnet and the flux provided by saidinput winding balance each other.
 3. The automatic balancing apparatusaccording to claim 2 wherein said movable magnet and said forcing coilare mounted on the same rotary shaft.
 4. An automatic balancingapparatus comprising a magnetic standard including a saturable magneticcore provided with an input winding, an output winding and a positivefeedback winding, and a movable magnet providing for said magnetic corea flux of a value corresponding to the angle of rotation of said movablemagnet; a self-oscillating circuit including a first amplifier toamplify the output from said output winding of said magnetic standard,and a circuit for positively feeding back the output from said firstamplifier to said positive feedback winding; a rectifier to rectify theoutput from said self-oscillation circuit; a second amplifier to amplifythe output from said rectifier; a forcing coil responsive to the outputfrom said second amplifier to drive said movable magnet until a balancedposition is reached where said flux provided by said movable magnet andthe flux provided by said input winding balance each other; a rate coilwound on the same frame as said forcing coil; and means to negativelyfeedback the output from said rate coil to the input of said secondamplifier.